Shrimp

Networks

All harvesters

• Pre-closure: 2009-2014
• Post-closure: 2016-2021

	Density	Modularity
pre-closure	0.4209184	0.1563785
post-closure	0.5110544	0.1858039

Shrimpers

	Density	Modularity
pre-closure	0.3129252	0.08896277
post-closure	0.2959184	0.09546118

Non-shrimpers

	Density	Modularity
pre-closure	0.337585	0.1553351
post-closure	0.4795918	0.182126

Changes in portfolios of shrimp harvesters

Entry and exit

Post closure, shrimp (css, csc), lobster-apprentice under 18 (lau), and elver dip net fyke 1 (e6) are replaced by menhaden (menc, menr), spat, and aquaculture, all of which are new license categories and don’t necessarily represent a shift in fisheries.

The proportion of licenses held by shrimpers didn’t appear to change dramatically by those who chose to continue in fisheries. Lobster was still the dominant target species by these harvesters.

Difference in difference estimator

Did the closure of the shrimp fishery impact the number of licenses held by harvesters?

# A tibble: 4 × 5
  term             estimate std.error statistic  p.value
  <chr>               <dbl>     <dbl>     <dbl>    <dbl>
1 (Intercept)         1.30     0.0469     27.8  1.91e-17
2 shrimp_harvester    1.47     0.0663     22.2  1.43e-15
3 closure             0.105    0.0663      1.58 1.29e- 1
4 did                -0.478    0.0937     -5.10 5.47e- 5

According to the DiD estimator, the closure did negatively impact those shrimpers in a statistically significant way. It may be worth noting that a significant number of harvester left fisheries entirely after the moratorium and we may need to figure out a way to incorporate exit and entry in the difference-in-difference estimation.